fix(tracing): capture span body exceptions and export SGP status=ERROR

[NiteshDhanpal]

Problem

Spans exported to SGP always show status=SUCCESS, even when the operation they represent failed.

Root cause, in three parts:

• The SGP span (scale_gp_beta) defaults status="SUCCESS" and only flips to "ERROR" inside its own __exit__ context manager. The agentex processor builds SGP spans via create_span(...) and flushes them directly, so __exit__ never runs.
• The agentex Span type (generated from the OpenAPI spec) has no status/error field.
• Trace.span() / AsyncTrace.span() ended spans in a bare finally, so a body exception was never recorded before the span was flushed.

Net effect: a failing operation is indistinguishable from a successful one in SGP.

Fix (SDK-only, no schema/backend change)

Capture → carry → map:

1. Capture — both context managers now except Exception as exc: set_span_error(span, exc); raise.
2. Carry — span_error.py stores the failure under the reserved span.data["__error__"] key, following the existing __span_type__/__source__ convention. data is a real field, so it survives model_copy(deep=True) and round-trips to both the SGP and agentex-native stores. (A first-class status/error field would require the OpenAPI → Stainless → backend → migration chain; this achieves the same SGP outcome without it.)
3. Map — _build_sgp_span() sets sgp_span.status = "ERROR" + error/error.type/error.message metadata when an error is present, matching SGP's native __exit__ shape.

Exceptions still propagate unchanged. asyncio.CancelledError / KeyboardInterrupt are intentionally not flagged (control flow, not failures) — broaden the except to BaseException if that changes.

Tests

tests/lib/core/tracing/test_span_error.py:

• set_span_error/get_span_error helpers (incl. list-shaped data no-op).
• Sync + async context managers record the error and re-raise; success path stays clean.
• _build_sgp_span maps error → status=ERROR + metadata; no-error path stays SUCCESS.

ruff check clean; new + existing tracing tests pass (40 passed).

🤖 Generated with Claude Code

Greptile Summary

This PR fixes silent status=SUCCESS on failing SGP spans by wiring exception capture into both Trace.span() / AsyncTrace.span() context managers and threading the captured error through to the SGP span builder.

• Capture: both sync and async context managers now except Exception as exc, call set_span_error(span, exc), and re-raise; non-Exception subclasses (asyncio.CancelledError, KeyboardInterrupt) intentionally bypass the handler.
• Carry: span_error.py stores the failure as span.data[\"__error__\"] = {\"type\": ..., \"message\": ...}, following the existing __span_type__/__source__ double-underscore convention; the value survives recursive_model_dump and model_copy(deep=True) since those preserve all dict keys.
• Map: _build_sgp_span calls sgp_span.set_error(error_type=..., error_message=...) when an error is present, flipping SGP status to \"ERROR\" and populating error metadata, matching what SGP's own __exit__ produces.

Confidence Score: 5/5

The change is safe to merge — it adds exception capture to both context managers and a minimal mapper in the SGP span builder, with no mutations to the processor pipeline, API contracts, or span flushing logic.

The three-part fix (capture → carry → map) is internally consistent: set_span_error writes a plain-dict value under a reserved key that survives recursive_model_dump (verified by reading model_utils.py) and model_copy(deep=True); the except/raise in both context managers correctly fires before the finally end_span call; and the SGP builder reads the error before returning the span. No pre-existing behavior is altered on the success path.

No files require special attention.

Important Files Changed

Filename	Overview
src/agentex/lib/core/tracing/span_error.py	New module providing set_span_error/get_span_error helpers; correctly handles None/dict/list-shaped span.data and follows the existing double-underscore reserved-key convention.
src/agentex/lib/core/tracing/trace.py	Adds except/raise around yield in both sync and async span() context managers; only Exception is caught (intentionally excludes CancelledError/KeyboardInterrupt), and the finally block always calls end_span, preserving existing behavior.
src/agentex/lib/core/tracing/processors/sgp_tracing_processor.py	_build_sgp_span now reads get_span_error and calls set_error on the SGPSpan when an error is present; the change is minimal, correctly ordered after start_time assignment, and does not affect the no-error path.
tests/lib/core/tracing/test_span_error.py	Covers helpers, sync/async context-manager capture, and _build_sgp_span mapping via a FakeSGPSpan; tests patch create_span so the real SGPSpan.set_error signature is not verified but the SDK contract is described accurately in the PR.

Sequence Diagram

%%{init: {'theme': 'neutral'}}%%
sequenceDiagram
    participant Caller
    participant Trace as Trace / AsyncTrace
    participant SpanError as span_error.py
    participant Processor as SGP Processor
    participant SGPSpan as SGPSpan (_build_sgp_span)

    Caller->>Trace: async with trace.span("op") as span
    Trace->>Trace: start_span() creates Span
    Trace-->>Caller: yields span

    alt Body raises Exception
        Caller->>Trace: raises Exception
        Trace->>SpanError: set_span_error(span, exc)
        SpanError->>SpanError: "span.data[__error__] = {type, message}"
        Trace->>Trace: re-raise
    end

    Note over Trace: finally block always runs
    Trace->>Trace: end_span(span)
    Trace->>Trace: recursive_model_dump preserves __error__
    Trace->>Processor: "on_span_end(span.model_copy(deep=True))"
    Processor->>SGPSpan: _build_sgp_span(span, env_vars)
    SGPSpan->>SpanError: get_span_error(span)
    SpanError-->>SGPSpan: dict or None

    alt Error present
        SGPSpan->>SGPSpan: set_error(error_type, error_message)
        Note over SGPSpan: status = ERROR
    else No error
        Note over SGPSpan: status remains SUCCESS
    end

    SGPSpan-->>Processor: SGPSpan with correct status
    Processor->>Processor: flush / upsert_batch

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sequenceDiagram
    participant Caller
    participant Trace as Trace / AsyncTrace
    participant SpanError as span_error.py
    participant Processor as SGP Processor
    participant SGPSpan as SGPSpan (_build_sgp_span)

    Caller->>Trace: async with trace.span("op") as span
    Trace->>Trace: start_span() creates Span
    Trace-->>Caller: yields span

    alt Body raises Exception
        Caller->>Trace: raises Exception
        Trace->>SpanError: set_span_error(span, exc)
        SpanError->>SpanError: "span.data[__error__] = {type, message}"
        Trace->>Trace: re-raise
    end

    Note over Trace: finally block always runs
    Trace->>Trace: end_span(span)
    Trace->>Trace: recursive_model_dump preserves __error__
    Trace->>Processor: "on_span_end(span.model_copy(deep=True))"
    Processor->>SGPSpan: _build_sgp_span(span, env_vars)
    SGPSpan->>SpanError: get_span_error(span)
    SpanError-->>SGPSpan: dict or None

    alt Error present
        SGPSpan->>SGPSpan: set_error(error_type, error_message)
        Note over SGPSpan: status = ERROR
    else No error
        Note over SGPSpan: status remains SUCCESS
    end

    SGPSpan-->>Processor: SGPSpan with correct status
    Processor->>Processor: flush / upsert_batch

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_{Reviews (2): Last reviewed commit: "fix(tracing): capture span body exceptio..." | Re-trigger Greptile}

[smoreinis]

can we target next instead of main here and also fix the diff to pass lint?